The present invention relates to a magnetic tape cassette, particularly to a magnetic tape cassette having an improved mistake erasure preventing device by which a "recordable" mode or an "unrecordable" mode can be established for the cassette.
A magnetic tape cassette is usually provided with an mistake erasure preventing device with which either a mode of making it possible to record information on the magnetic tape in the cassette or a mode of making it impossible to record information thereon is set. For example, if a magnetic tape cassette has information recorded on the magnetic tape which is desired to be retained for a long period of time, the mistake erasure preventing device is manipulated to prevent the mistake erasure of the tape.
Various conventional mistake erasure preventing devices are known. In one such device, a break-out tab is provided in an appropriate position on the outside surface of the body of the magnetic tape cassette in such a manner that the tab can be removed to expose a detection hole. In another arrangement, a slidable or rotatable member is manipulated to expose a detection hole in the outside surface of the magnetic tape cassette. The recording/playback apparatus is set in the appropriate mode by a detector movable into the detection hole, as disclosed in Japanese Utility Model Application No. 38181/79 and Japanese Unexamined Published Utility Model Applications Nos. 98289/86 and 28256/80.
However, these conventional mistake erasure preventing devices have a problem that it is often difficult to quickly determine whether or not the cassette is in the "re-recordable". Even if the magnetic tape cassette is provided with an indicator which makes it easy to see whether or not the magnetic tape cassette is in the "re-recordable" mode, the cassette has a problem that the indicator cannot be easily seen in some position of the cassette.